Former UBS trader Kweku Adoboli, who was found guilty of fraud at a London court on Tuesday, cost the Swiss bank £1.4bn ($2.3bn).

At one point, he was at risk of causing the bank record-breaking losses of £7.5bn ($12bn).

Prosecutors said the billion dollar fraudster was motivated by his bonus, his status and his ego.

Sue Patten, head of fraud at the Crown Prosecution Service, told Sky News: "This is a fraud on a colossal scale in terms of its value and I'm not sure that there has been certainly in England and Wales a case on this scale."

It was in September 2011 when staff at UBS offices in the City of London became suspicious that Adoboli, 32, was exceeding his trading limits.

Transcripts of phone calls between accountants and Adoboli were released to the court.

On September 14, accountant William Steward called to say: "Everyone's getting very excited about this credit exposure ...

"Is it a huge number of trades booked ... any chance you could send me the details of the average price and stuff?"

Adoboli was hesitant but responded: "Em yeah, sure em, I'll, I'll just have to pull them out, give me a little bit."

But throughout the day William Steward became increasingly worried that his trader had made large one-way bets and exposed the bank to huge losses.

Image:Adoboli leaving court at an earlier hearing

He called back saying: "It seems a bit strange because we're seeing a debit like an asset exposure with iSHARES and with SocGen which seems a bit strange because ... if they're the two sides of the same trade I can't understand why we'd have an asset on both sides."

Adoboli replied: "Em ... if you could explain to me what you understand an asset to be?"

The investment banker realised the game was up. As soon as he had put down the phone he walked out of the office.

An hour after fleeing the office he sent what has been described as "a bombshell email".

It said: "Dear Will, it is with great stress and disappointment that I write this mail.

"First of all, the EFT trades that you see on the ledger are not trades that I have done with a counterparty as I previously described.

"I used the bookings as a way to suppress the PnL losses that I have accrued through off book trades that I made ..."

He went on to explain that: "…an escalation in the eurozone crisis cost me the losses you will see when the EFT bookings are cancelled.

"The aim had been to try and make the money back before the September expiry date came through but I clearly failed. "

He added: "I take full responsibility for my actions and the s**t storm that will now ensue.

"I am deeply sorry to have left this mess for everyone and to have put my bank and my colleagues at risk. Thanks, Kweku."

Adoboli was called back to the office, where overnight it was discovered he had gambled huge sums. UBS called the police.

In court Adoboli was found guilty of two counts of fraud by abuse of position. He was found not guilty of four counts of false accounting.

In the witness box he tearfully claimed other staff used similar methods and managers encouraged rule-bending in pursuit of profits.

Summing up, Brian Keith told the jury not to let any views they may have about bankers to cloud their judgement.

He said: "You don't need me to tell you that this case has been no ordinary trial.

"How could it have been when the man you're trying was an apparently respectable trader at a famous investment bank whose trading on behalf of the bank led to a loss so colossal that exceeded $2bn?"

He went on: "There's been a lot of talk in recent years about the bonus culture, failing banks having to be bailed out."

He added that there were always two sides to every argument.

He told the jury they were not there to find someone responsible at all costs for the loss that UBS had suffered.